Intermittent fasting for beginners can seem daunting. You may wonder whether long periods without food will be sustainable and compatible with your lifestyle, or that you will feel too hungry during your fasting periods. The good news is that there are many different types of intermittent fasting, so if you are looking to embark on a plan you can choose whichever style fits your lifestyle best.
You should consider what you hope to achieve through intermittent fasting – are you hoping to see an improvement in your sleep quality? Or perhaps you are hoping to lose weight. This can affect which type of intermittent fasting plan you go for, as some kinds have larger amounts of research behind them.
We’ve spoken to the experts to bring you a comprehensive guide to intermittent fasting for beginners, along with some handy tips to consider when making large changes to your diet.
What happens during intermittent fasting?
Dr Nirusa Kumaran, Medical Director and Founder of Elemental Health Clinic (opens in new tab), told Live Science: “One main method by which intermittent fasting can help is by driving a process called ketosis. Ketosis is where our body burns ketones instead of glucose for energy. There have been reported health benefits of going into ketosis such as improving metabolism and reducing inflammation.”
Ketosis has been shown to have a positive trend in weight loss and reversal of cardiometabolic syndrome, according to one study in Current Nutritional Reports (opens in new tab). As well as fasting, the state of ketosis can be triggered by the ‘keto diet’ – a low-carbohydrate, high-fat diet.
Ketosis is just one of the changes that happens to the body while intermittent fasting. Kumaran adds: “Other changes that occur in the body include increased levels of growth hormone which can help with fat loss and muscle gain, improved insulin sensitivity, meaning your blood sugar gets processed quickly and stored fat can be burned for energy, and cell repair – mitochondria and cells are shown to repair themselves through a process called autophagy, where effectively damaged cells are removed and replaced with new cells.”
Which type of intermittent fasting is best for beginners?
There are several different types of intermittent fasting, and it might be worth experimenting to find which works best for you. If your schedule is fairly flexible, you might be able to sustain a more intensive fasting style, such as time restricted eating or alternate day fasting. If you have a family to work around, you may find 5:2 fasting less disruptive, as you can still enjoy family meals 70% of the time, and focus on your fast the rest of the time.
Kumaran outlines the main types of fasting:
1) Time Restricted Eating – e.g 20:4, 16:8, 14:10; 12:12 – the first number represents the number of hours you fast for, while the second number represents the number of hours you have as an eating window. So for example with 16:8, you fast for 16 hours and eat within an eight hour window. For some people, this means skipping breakfast, and eating lunch and dinner, however others may choose to skip their evening meal instead.
14:10 and 12:12 tend to be the best for those new to intermittent fasting, because they are less restrictive in terms of when you can eat.
2) 5:2 Fasting – In this method, you can eat normally for five days a week, but on two non-consecutive days you consume 500-600 calories a day.
3) One meal a day – This is where you eat only one meal a day, and get all your calories and nutrition from that meal.
4) Alternate Day Fasting – With this fasting method, you eat nothing on your fasting days – these alternate during the week. For example, if you choose to fast on Monday, Wednesday, Friday and Sunday in one week, then you eat normally on the days in-between, and as such this pattern continues.
A review in Nutrition Reviews (opens in new tab) indicates that intermittent fasting can be effective in reducing body weight in people of every size, with most studies focusing on alternate-day fasting or whole-day fasting trials. As such, fasting for weight loss may be better suited to these styles of fasting.
It is worth noting that some types of intermittent fasting are better suited to men than women. Intermittent fasting for women requires a slightly different approach due to differences in women’s hormonal makeup throughout their menstrual cycle.
Intermittent fasting for beginners: Top tips
A study in the Annual Review of Nutrition journal also found that the time windows used for intermittent fasting can impact sleep and overall health. Parts of our body’s internal clock are often triggered by feeding, as well as the amount of light you see. As such, fasting overnight (when you’d expect to be asleep) can have positive cardiometabolic and healing effects on the body, while eating during the time your body expects to be sleeping can disrupt these processes and cause fluctuations in energy levels. If sleeping well is your goal, then a time restricted feeding plan could be best.
- Related: Is breakfast important? (opens in new tab)
- Related: Four possible benefits of fasting (opens in new tab)
Kumaran also recommends caution with intermittent fasting if you have underlying health conditions, although she notes it can be undertaken under the supervision of a medical professional or nutrition expert.
“There are many medical conditions where it may be safe for you to undertake intermittent fasting when under the guidance of a qualified medical professional,” she says. “These can include cardiovascular diseases, diabetes, metabolic syndrome, and even some cancers.” There may also be certain considerations when it comes to women's health.
Gershuni, V. M., Yan, S. L., & Medici, V. (2018). Nutritional Ketosis for Weight Management and Reversal of Metabolic Syndrome. Current Nutrition Reports, 7(3), 97–106. https://doi.org/10.1007/s13668-018-0235-0 (opens in new tab)
Patterson, R. E., & Sears, D. D. (2017). Metabolic Effects of Intermittent Fasting. Annual Review of Nutrition, 37(1), 371–393. https://doi.org/10.1146/annurev-nutr-071816-064634 (opens in new tab)
Tinsley, G. M., & La Bounty, P. M. (2015). Effects of intermittent fasting on body composition and clinical health markers in humans. Nutrition Reviews, 73(10), 661–674. https://doi.org/10.1093/nutrit/nuv041 (opens in new tab)